Holeless Curtain Wall Mullion Connection

ABSTRACT

A mullion connection system for resisting wind load reactions using a connection clip structurally engaged with a mullion without a hole or a fastener penetrating into the mullion surface. The connection clip can undergo stress-free vertical sliding relative to the mullion along the entire length of the mullion without impairing the structural connection strength; therefore, the building construction tolerance in the vertical direction is eliminated as a design consideration of the curtain wall system. The design also eliminates the need for pre-fabricating mullion holes for the connection locations. The design does not require the pre-determination of the elevation of the connecting point and thus is most beneficial for a curtain wall renovation project where the available locations in the building structure for structural connection cannot be determined prior to the demolition of the existing wall. The uninterrupted mullion tube cavities can be conveniently utilized for inter-floor distribution of utility lines.

FIELD OF THE INVENTION

This invention relates to exterior curtain wall connection design. The design is applicable to either a solid mullion or a split mullion condition.

BACKGROUND OF THE INVENTION

An exterior curtain wall system consists of three major components, namely, wall panels providing weather protection, mullions providing structural support to the wall panels, and mullion connection systems providing a structural connection between the mullions and a building structural element. Due to the fact that there is a gap between the acceptable construction tolerance for the curtain wall and the acceptable construction tolerance for the building structural element, the mullion connection system must be designed to absorb the construction tolerance of the building structural element in all three directions (i.e., up/down, in/out and left/right). The most difficult adjustment is in the up/down direction due to the following factors: (a) tolerance due to dead load deflection of spandrel beam (e.g., 12.7 mm or 0.5″); (b) tolerance in floor slab thickness (e.g., 3.2 mm or 0.125″); (c) floor sloping tolerance from side to side (e.g.,) 0.1°; (d) accumulated height tolerance due to floor height tolerance (e.g., 3.2 mm or 0.125″ per floor); (e) additional required in-service functions of allowing for inter-floor deflection (e.g., 19 mm or 0.75″) and long term dead load creep in the concrete floor slab and/or concrete column (e.g., 3.2 mm or 0.125″ per floor). The mullion connection system normally consists of a connection clip on each side of the mullion bolted together through the mullion tube and a structural bridge connecting between the connection clips and the building structural element. The problems of current mullion connection systems in adjusting for construction tolerance in the up/down direction are listed below.

(1) For a solid vertical mullion system, a vertical slotted hole is provided either in the mullion connection clip or in the mullion webs (U.S. Pat. Nos. 6,591,562 and 6,598,361). The length of the slotted hole is designed to accommodate the construction tolerance of the building structural element, the inter-floor live load deflection, and the effect of long term dead load concrete creep as stated in the job specification. Out of tolerance conditions experienced in the field often result in structurally compromising modifications being employed without the approval of a structural engineer. If the out of tolerance condition is still erectable but leaves inadequate room for inter-floor deflection, the condition would be unchecked and the structural integrity in the service condition would be compromised. In addition, the wind load reaction would create a point bearing condition of the mullion bolt on the edge of the slotted hole producing an overstress condition. This overstress condition is largely ignored except the use of a load transferring block inside the mullion tube in conjunction with the slotted hole being in the mullion web in a more advanced design. In addition, depending on the condition of the contacting surface, being too tight on the mullion bolt might disable the sliding function required for the inter-floor deflection while being too loose might impair the structural integrity of the connection system due to the danger of walking and loosening of the bolt nut. Therefore, a proper torque for tightening the bolt is normally specified for the design, but it is difficult to police the execution in the field. In conclusion, the proper installation of the slotted hole design is almost impossible to police and ensure in the field.

(2) For a unitized split mullion system, a mullion connection clip with up/down adjustable setting bolt is shop-fastened to the mullion near the mullion end. After the unit is adjusted in the two horizontal directions, the final up/down adjustment is done by the adjustable setting bolt. This connection design is not affected by the inter-floor deflection or concrete creep. However, the amount of adjustment will affect the connection strength and it is designed for the maximum construction tolerance in the job specification. Similar to the above discussion of the slotted hole design, a structurally compromised condition with over-adjustment due to an out of tolerance situation is largely ignored in the field.

(3) As an example, using a floor sloping tolerance of 0.1° on a 30.48 m or 100′ wide wall, the calculated height tolerance is 53.2 mm or 2.094″ from side to side. Existing mullion connection systems are incapable of making such a large tolerance adjustment without impairing structural integrity and the curtain wall erection has to ignore the sloping tolerance by following the slope.

(4) As an example, using a floor height tolerance of 3.2 mm or 0.125″ on a 100-story building, the accumulated height tolerance is 320 mm or 12.5″. It is necessary to design the system to absorb this tolerance on a per floor basis.

(5) As an example, using a dead load deflection of 12.7 mm or 0.5″, a slab thickness tolerance of 3.2 mm or 0.125″, and a floor height tolerance of 3.2 mm or 0.125″, the required total tolerance adjustment per floor is 19 mm or 0.75″. Connection systems from curtain wall suppliers in today's market are commonly designed with a maximum tolerance adjustability of ±19 mm or ±0.75″. Designing for a higher adjustability would either impair structural integrity or become too expensive. However, the above slab thickness tolerance is considered to be too tight to execute by the slab contractor and the above floor height tolerance is considered to be too tight to execute by the building frame contractor. Therefore, an out of tolerance condition becomes unavoidable.

Therefore, there is a need for an improved mullion connection system that can assure the structural integrity of the mullion connection while allowing a much higher construction tolerance in the vertical direction.

SUMMARY OF THE INVENTION

To achieve the goal of a mullion connection design being able to tolerate a large construction tolerance in the vertical direction in accordance with the purpose of the invention as embodied and broadly described herein, the present invention provides a mullion connection system with the construction tolerance adjustability in the vertical direction being independent of other curtain wall functions.

Several objectives of the present invention include the following items.

-   1. To provide a mullion connection system to tolerate a large     construction tolerance without using a slotted hole in the mullion. -   2. To provide a mullion connection system to tolerate a large     construction tolerance without impairing the structural integrity of     the connection. -   3. To provide a mullion connection system without a bolt penetrating     through the mullion tube to allow the use of the uninterrupted     mullion tube cavity for the distribution of utility lines.

These objectives of the present invention and other objectives will become evident to those of ordinary skill in the art after reading the following detailed description of preferred embodiments.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,

FIG. 1 is a typical conceptual cross-sectional view of a mullion connection system in the rear mullion flange for a solid mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between a female joint in the mullion and a male joint in the connection clip;

FIG. 2 is a typical conceptual cross-sectional view of a mullion connection system in the rear mullion flange for a solid mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between a wide female joint in the mullion and a male joint in the connection clip;

FIG. 3 is a typical conceptual cross-sectional view of a mullion connection system in the rear mullion flange for a solid mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between a male joint in the mullion and a female joint in the connection clip;

FIG. 4 is a typical conceptual cross-sectional view of a mullion connection system in the rear mullion flange for a solid mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between two off-setting double female joints, one in the mullion and one in the connection clip;

FIG. 5 is a typical conceptual cross-sectional view of a mullion connection system on the mullion webs for a solid mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between a female joint in the mullion and a male joint in the connection clip;

FIG. 6 is a typical conceptual cross-sectional view of a mullion connection system on the mullion webs for a solid mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between the mullion and the connection clip with each having a pair of male and female joints;

FIG. 7 is a typical conceptual cross-sectional view of a mullion connection system in the rear mullion flange for a split mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between a male joint in the mullion and a female joint in the connection clip;

FIG. 8 is a typical conceptual cross-sectional view of a mullion connection system in the rear mullion flange for a split mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between two off-setting double female joints, one in the mullion and one in the connection clip;

FIG. 9 is a typical conceptual cross-sectional view of a mullion connection system on the mullion webs for a split mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between a female joint in the mullion and a male joint in the connection clip;

FIG. 10 is a typical conceptual cross-sectional view of a mullion connection system on the mullion webs for a split mullion condition incorporating an embodiment of the present invention with the structural inter-locking engagement between the mullion and the connection clip with each having a pair of male and female joints;

FIG. 11 is a typical conceptual side view of the mullion connection system incorporating an embodiment of the present invention suitable for a dead loaded mullion design in a low-rise building.

FIG. 12 is a typical conceptual side view of the mullion connection system incorporating an embodiment of the present invention suitable for a normal curtain wall mullion design in a high-rise building.

There are many possible variations of the shape and the location of each matching inter-locking male/female joints. The above Figures only show a few possible variations to illustrate the concept of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

In order to better explain the working principles of the invention, the following terminology will be used herein:

Mullion: one of a plurality of spaced apart structural members generally in the vertical direction used to structurally support the weather sealing exterior wall panels;

Mullion Connection System: a structural system designed to transfer the reaction forces on the mullion due to dead load and wind load into a structural supporting element within the building structure.

Connection Clip: the first component of the Mullion Connection System designed to transfer the reaction forces on the mullion to a second component of the Mullion Connection System; and

Structural Bridge: the second component of the Mullion Connection System designed to structurally connect between the Connection Clip and a structural supporting element of the building.

FIG. 1 illustrates a typical cross-sectional view of an embodiment of the mullion connection system 10 comprising a vertical solid mullion 11, a connection clip 12, and a structural bridge 13. The mullion 11 is used to support the exterior wall panels 16. A male joint 14 is provided on each side of the connection clip to cause structural engagement with the matching female joints 15 on the mullion 11. It can be easily understood that free relative sliding between the connection clip 12 and the mullion 11 is achieved for adjusting any amount of construction tolerance without a bolt penetrating through the mullion 11. It can also be easily understood that the engaged connection strength against wind load reaction is a constant and independent of the final adjusted location of the connection clip 12 as long as it is within the length of the mullion 11. The mullion tube cavity 17 can be utilized as an inter-floor conduit for vertical distribution of utility lines such as power or communication cables or water supplying tubes. The mullion tube cavity 17 can be further compartmented for other purpose such as isolating one area for splicing two mullion segments at a butt joint with splice tube and fasteners (not shown). The connection clip 12 is fastened to the structural bridge 13 for connection to a structural element of the building structure (not shown). The installation of the mullion connection system involves the following four simple steps: (1) position the end of the mullion 11 away from the connection point at a minimum distance for the maximum intended tolerance adjustment; (2) slide the connection clip 12 into engagement with the mullion 11 from the mullion end and slide the connection clip 12 to a location near the connection point; (3) fasten the connection clip 12 to the structural bridge 13; (4) slide the assembly of the connection clip 12 and the structural bridge 13 up or down to the connection point and fasten the structural bridge to the structural element of the building structure. The profile of the structural bridge 13 can be selected from many available shapes to fit the requirement at the connection point with the structural element of the building structure. For example, a popular structural element of the building structure is a slab edge pre-set steel embed (not shown) and a simple steel angle clip can be used as the structural bridge 13 for fastening to the steel embed by welding or screws.

FIG. 2 shows a design variation of FIG. 1. A partition member 19 is provided to create two mullion cavity spaces 17 a and 17 b resulting in a wide female joint 15 in the mullion 11 for engaging the male joint 14 in the connection clip 12. Sliding guide lips 18 are provide on the partition member 19. In this arrangement, the cavity space 17 a can be used for the mullion splice tube and fasteners at the mullion butt joint (not shown) and the cavity 17 b can be used for open channel utility wiring operation without wire-fishing. After the utility lines have been installed, the gap of the rear mullion flange in the interior visual region can be easily covered with a snap-on cover. The other functions and the erection procedures remain the same as explained for the embodiment shown FIG. 1.

FIG. 3 shows a design variation of FIG. 2. Two male joints 14 a are provided in the mullion 11 for structural engagement with the two matching female joints 15 a in the connection clip 12. The other functions are the same as explained for the embodiment shown in FIG. 2, and the erection procedures remain the same as explained for the embodiment shown in FIG. 1.

FIG. 4 shows another design variation of FIG. 3. Two female joints 15 c are provided in the mullion 11 for structural engagement with the matching female joints 15 a in the connection clip 12. The other functions are the same as explained for the embodiment shown in FIG. 2, and the erection procedures remain the same as explained for the embodiment shown in FIG. 1.

FIG. 5 shows another design variation of FIG. 2. On each side of the mullion 11, a female joint 15 d is provided in the web area of the mullion 11 for structural engagement with the matching female joint 15 e in a connection clip 12. The other functions are the same as explained for the embodiment shown in FIG. 2 except requiring wire-fishing in the cavity 17 b, and the erection procedures remain the same as explained in FIG. 1.

FIG. 6 shows another design variation of FIG. 2. On each side of the mullion 11, a female joint 15 f and a male joint 14 c are provided in the web area of the mullion 11 for structural engagement with the matching female joint 15 e and male joint 14 d in a connection clip 12. The other functions are the same as explained for the embodiment shown in FIG. 2 except requiring wire-fishing in the cavity 17 b, and the erection procedures remain the same as explained for the embodiment shown in FIG. 1.

FIG. 7 illustrates a typical cross-sectional view of an embodiment of a mullion connection system 20 comprising two vertical split mullions 11 a, a connection clip 12, and a structural bridge 13. The mullions 11 a are used to support the exterior wall panels 16. A female joint 15 g is provided on each side of the connection clip to cause structural engagement with the matching male joints 14 f on each of the split mullions 11 a. If the split mullions 11 a are made to be continuous over multiple floors, then the mullion tube cavities 17 c can be used for vertical distribution of utility lines. The other functions and the erection procedures remain the same as explained for the embodiment shown in FIG. 1.

FIG. 8 shows a design variation of FIG. 7. In this embodiment, a female joint 15 h is provided on each of the split mullions 11 a to cause structural engagement with the matching female joints 15 g on the connection clip 12.

FIG. 9 shows another design variation of FIG. 7. In this embodiment, a female joint 15 d is provided in the web area of each of the split mullions 11 a to cause structural engagement with the matching male joint 14 b on each of the connection clips 12.

FIG. 10 shows another design variation of FIG. 7. In this embodiment, a female joint 15 f and a male joint 14 c are provided in the web area of each of the split mullions 11 a to cause structural engagement with the matching female joint 15 e and male joint 14 d on each of the connection clips 12.

FIG. 11 shows the conceptual side view of the mullion connection system 10 or 20. The wall panels 16 are supported on the mullion 11 or 11 a. The connection clip 12 is structurally engaged with the mullion 11 or 11 a to resist wind load reaction and is free to slide up or down for a construction tolerance adjustment. The connection clip 12 is fastened to the structural bridge 13 with fasteners 21. After sliding the assembly of 12 and 13 up or down to the contacting point with the structural element in the building structure, the structural bridge 13 is fastened to the structural element (not shown). This condition is suitable for a dead-loaded mullion design and it can accommodate any amount of floor live load deflection carried to the structural bridge 13 due to the ability of stress-free sliding of the connection clip 12 in the vertical direction.

FIG. 12 shows the same conceptual side view of the mullion connection system 10 or 20 except a dead load block 22 is placed in contact with the top end of the connection clip 12 and fastened to the mullion 11 or 11 a with fasteners 23 to transfer the dead load reaction of the mullion segment onto the connection clip 12. This design is suitable for a regular curtain wall mullion design.

From the above discussions, it becomes apparent that all three inventive objectives are achieved. The present invention eliminates the need of imposing a non-practical requirement of the construction tolerance in the vertical direction on other trades (e.g., floor slab and building frame contractors). Benefits of the present invention to a curtain wall contractor include: (1) eliminating the need of field measurements in the vertical direction; (2) eliminating the need of shop fabricating the slotted hole in the mullion web or in the connection clip, or the need of shop installing the expensive device for field adjustment in the case of a unitized system; (3) providing an easy remedy for out-of-tolerance problems in the in/out direction (e.g., if the distance between the mullion and the slab edge is large for a regular on-slab connection, the connection clip 12 can be slid down below the slab and the structural bridge 13 can be easily changed to a structural steel shape extended to the spandrel beam for a welded connection); (4) eliminating the need for piece-wise shop fabrication of mullions in case of a design with changing elevations along the slab edge such as the ramp of a parking structure; (5) eliminating the need for pre-design field investigation and measurements for available anchoring locations in a curtain wall renovation project (sometimes impossible prior to the removal of the existing wall). There are various possible design variations in the shape and location for the structural engaging male/female joints. There are also various possible design variations in the shape for the connection clip 12. There are also various possible design variations in the shape for the structural bridge 13, as well as in the method of fastening it to the connection clip 12 and the structural element in the building structure.

Although preferred embodiments of the invention have been described in detail herein and illustrated in the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments and that various changes and modifications may be effected therein without departing from the scope or spirit of the invention. 

1. A mullion connection system providing a structural connection between a mullion and a building structural element comprising: a connection clip engaged with said mullion, wherein said connection clip is slidably engaged with said mullion using at least one set of matching male and female joints.
 2. The mullion connection system of claim 1, further comprising a structural bridge connected to said connection clip, wherein said structural bridge is connected to said building structural element.
 3. The mullion connection system of claim 1, further comprising a dead load block positioned in contact with the top end of said connection clip and secured to said mullion.
 4. The mullion connection system of claim 1, wherein said connection clip is engaged with said mullion without using a fastener penetrating said mullion.
 5. The mullion connection system of claim 1, wherein the vertical position of said connection clip relative to said mullion is adjustable to any location along the length of said mullion.
 6. The mullion connection system of claim 1, further comprising an uninterrupted mullion cavity.
 7. The mullion connection system of claim 6, further comprising utility lines distributed through said uninterrupted mullion cavity.
 8. A mullion connection system providing a structural connection between mullions and a building structural element comprising: a first mullion; a first connection clip engaged with said first mullion, wherein said first connection clip is slidably engaged with said first mullion using at least one set of matching male and female joints; a second mullion parallel to said first mullion; and a second connection clip engaged with said second mullion, wherein said second connection clip is slidably engaged with said second mullion using at least one set of matching male and female joints. 